<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
        <link rel="stylesheet" href="../script/bootstrap-3.3.7.min.css">
            <style type="text/css">
                img[src="img/img2.jpg"] {
                    opacity:0.4;
                }
                img[src="img/img.jpg"]:hover{
                    opacity: 0.4;
                }

            </style>
</head>
<body>
<div class="container">
    <div class="row">
        <div class="col-md-4 col-md-offset-2">
            <div>
                <p style="display: block;font-weight: bold">
                    opacity 来设定透明度。opacity 属性能够设置的值从 0.0 到 1.0。值越小，越透明</p>
            </div>
            <div>
                <img src="img/img2.jpg">
            </div>
        </div>

    </div>
<div class="page-header"></div>
        <div class="row">
        <div class="col-md-4 col-md-offset-2">
            <div>
                <p style="visibility: visible;font-weight: bold">
                    当指针移动到图像上时，图像是透明的
                </p>
            </div>
            <div>
                <img src="img/img.jpg">
            </div>
        </div>

    </div>

</div>


</body>
</html>